Typical microscope slides of the prior art include a "frosted" portion as a marking surface. This frosted area is created by sandblasting, acid etching, mechanical abrading, or other methods of roughening the surface of the glass so that a permanent marking surface is created to accept a marking by a pen, pencil, or other marking instrument. All of these techniques create a frosted surface by removing material from the glass surface, therefore necessarily resulting in a marking surface which is recessed from, or certainly no higher than, the surface of the glass. Furthermore, such frosted glass, while providing a matte surface on the glass, does not result in a marking surface having a pronounced background to contrast with information to be written thereon.
"Double frosted" or "double etched" slides, having such marking surfaces on both sides of the slide, are also known to the prior art.
The prior art also includes slides having a marking surface formed of a coating of resinous material which is pigmented and porous, and dries to a matte finish. The porosity of the resinous material makes it receptive to marking while the pigmentation enhances visibility of such marking. U.S. Pat. No. 4,481,246 discloses a slide of this type having a raised marking surface formed of pigmented resinous material, such as an epoxy resin, which dries to a matte finish and is absorptive and retentive of marking ink.
U.S. Pat. No. 4,679,914 discloses a microscope slide having on one side a frosted marking surface, and on the opposite side a raised resinous marking surface which is a) absorptive and receptive to marking materials, b) pigmented to provide a visual contrast to such marking surface, c) resistant to a variety of laboratory solvents, reagents, stains or chemicals, and d) susceptible of being produced in a variety of colors to facilitate color coding. Thus, the slide disclosed in the '914 patent has a writing surface on both sides of the slide, one being a raised resinous marking surface and the other being a frosted marking surface.
An object of this invention is to provide a microscope slide having contrastingly colored coatings on opposite sides which are positioned generally behind each other at a marking region of the slide such that the contrasting coatings are in an overlying relationship with each other, and in which at least one of the contrasting coatings is opaque and scratchable with a pointed scribe so that upon scribing, the scratchable coating is removed and the contrastingly colored coating from the opposite side of the slide is visible through the scribed area of the scratchable coating providing a high level of contrast for the scribed marking. At least one of the coatings, such as the scratchable coating, can also be marked with a pen, pencil or the like if desired. In a preferred form of the invention, each of the contrastingly colored coatings is pigmented and the coating on the side opposite to the scratchable coating is opaque.